Lithium secondary battery with improved safety

Abstract

An electrolyte composition and a lithium secondary battery including the same are disclose herein. The electrolyte composition has improved high temperature safety. In some embodiments, the electrolyte composition includes an additive including a compound represented by Formula 1. Each R 1 is independently a single bond, an alkylene group having 1 to 10 carbon atoms, or each R 2 is independently a double or triple bond including 2 carbon atoms, each R 3 is independently hydrogen or an alkyl group having 1 to 4 carbon atoms, and a is an integer of 1 to 10. The additive may reinforce an SEI layer on the surface of an electrode, thereby having advantages of improved storage and lifetime characteristics at a high temperature and a decreased amount of gas generated in the battery.

The invention claimed is: 
     
       1. An electrolyte composition, comprising:
 a non-aqueous organic solvent; 
 a lithium salt; and 
 an additive comprising a compound represented by Formula 1: 
 
       
         
           
           
               
               
           
         
         wherein, 
         each R 1  is independently a single bond, an alkylene group having 1 to 10 carbon atoms, or 
       
       
         
           
           
               
               
           
         
         each R 2  is independently a double or triple bond including 2 carbon atoms, 
         each R 3  is independently hydrogen or an alkyl group having 1 to 4 carbon atoms, and 
         a is an integer of 1 to 10. 
       
     
     
       2. The composition of  claim 1 , wherein each R 1  is independently a single bond, a methylene group, an ethylene group, a propylene group, or 
       
         
           
           
               
               
           
         
         each R 3  is e independently hydrogen or a methyl group, and 
         a is an integer of 1 to 5. 
       
     
     
       3. The composition of  claim 1 , wherein the compound represented by Formula 1 comprises one or more compounds of Structural Formulas 1 to 8 below: 
       
         
           
           
               
               
           
         
         
           
           
               
               
           
         
       
     
     
       4. The composition of  claim 1 , wherein the additive is present in an amount of 0.01 to 5 wt % with respect to the total weight of the electrolyte composition. 
     
     
       5. The composition of  claim 1 , wherein the lithium salt comprises one or more selected from the group consisting of LiCl, LiBr, LiI, LiClO 4 , LiBF 4 , LiB10Cl 10 , LiPF 6 , LiCF 3 SO 3 , LiCF 3 CO 2 , LiAsF 6 , LiSbF 6 , LiAlCl 4 , CH 3 SO 3 Li, (CF 3 SO 2 ) 2 NLi, and (FSO 2 ) 2 NLi. 
     
     
       6. The composition of  claim 1 , wherein the non-aqueous organic solvent comprises one or more selected from the group consisting of N-methyl-2-pyrrolidinone, ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, 7-butyrolactone, 1,2-dimethyoxy ethane, tetrahydroxy franc, 2-methyl tetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl citrate, phosphoric acid triester, trimethoxy methane, a dioxolane derivative, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, a propylene carbonate derivative, a tetrahydrofuran derivative, ether, methyl propionate, and ethyl propionate. 
     
     
       7. A lithium secondary battery, comprising:
 an electrolyte assembly comprising a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode; and 
 an electrolyte composition comprising a non-aqueous organic solvent, a lithium salt, and an additive comprising a compound represented by Formula 1: 
 
       
         
           
           
               
               
           
         
         wherein, 
         each R 1  is independently a single bond, an alkylene group having 1 to 10 carbon atoms, or 
       
       
         
           
           
               
               
           
         
         each R 2  is independently a double or triple bond including 2 carbon atoms, 
         each R 3  is independently hydrogen or an alkyl group having 1 to 4 carbon atoms, and 
         a is an integer of 1 to 10. 
       
     
     
       8. The battery of  claim 7 , wherein the positive electrode comprises:
 a positive electrode current collector; and 
 a positive electrode mixture layer which is formed on the positive electrode current collector, 
 wherein the positive electrode mixture layer comprises a lithium metal oxide represented by Formula 2, a lithium metal oxide represented by Formula 3, or a combination thereof:
   Li x [Ni y Co z Mn w M 1   v ]O 2   [Formula 2]
 
   LiM 2   p Mn (2−p) O 4   [Formula 3]
 
 
 In Formulas 2 and 3, 
 M 1  is one or more elements selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo, 
 x, y, z, w and v are respectively 1.0≤x≤1.30, 0.5≤y<1, 0<z≤0.3, 0<w≤0.3, and 0≤v≤0.1, wherein y+z+w+v=1, 
 M 2  is Ni, Co or Fe, and 
 p is 0.05≤p≤0.6. 
 
     
     
       9. The battery of  claim 8 , wherein the lithium metal oxide comprises one or more selected from the group consisting of LiNi 0.8 Co 0.1 Mn 0.1 O 2 , LiNi 0.6 Co 0.2 Mn 0.2 O 2 , LiNi 0.9 Co 0.05 Mn 0.05 O 2 , LiNi 0.6 Co 0.2 Mn 0.1 Al0.1O 2 , LiNi 0.6 Co 0.2 Mn 0.15 Al 0.05 O 2 , LiNi 0.7 Co 0.1 Mn 0.1 Al 0.1 O 2 , LiNi 0.7 Mn 1.3 O 4 , LiNi 0.5 Mn 1.5 O 4 , and LiNi 0.3 Mn 1.7 O 4 . 
     
     
       10. The battery of  claim 7 , wherein the negative electrode comprises:
 a negative electrode current collector; and 
 a mixture layer which is formed on the negative electrode current collector, 
 wherein the mixture layer comprises a negative electrode active material, and 
 wherein the negative electrode active material comprises one or more carbon materials selected from the group consisting of natural graphite, artificial graphite, expanded graphite, non-graphitizing carbon, carbon black, acetylene black, and Ketjen black. 
 
     
     
       11. The battery of  claim 10 , wherein the negative electrode active material further comprises one or more silicon materials selected from the group consisting of silicon (Si), silicon carbide (SiC) and silicon oxide (SiOq, 0.8≤q≤2.5). 
     
     
       12. The battery of  claim 11 , wherein the silicon material is present in an amount of 1 to 20 wt % with respect to the total weight of the negative electrode active material.